There’s a perfect foreboding moment near the beginning of “The Lucky Ones” that gets at what I take to be the heart of the matter.

Abigail Bengson, who narrates much of the quasi-autobiographical electro-folk singspiel, is painting the scene of her childhood in a “hippy tolerant” extended family. Her mother and father and aunt all teach at the super-crunchy Blue Mountain School in a “part of Vermont that happens to be in Maine”; their five children, from teenagers to young adults, make a seemingly undifferentiated puppy pile, frolicking happily.

It is morning. Eggs and bacon are frying. The new school year is opening wide. Together these good people sing a lovely chorale, their individual voices in harmony with the whole.

“But of course what it really sounds like is this,” Abigail says, interrupting. When we then hear it unmusicalized, as clashing lines of dialogue, it’s just awful chaos.

The full impact of that chaos will not emerge until later in the show, an Ars Nova production that opened on Saturday night at the Connelly Theater in the East Village. But the sweet glaze of memory, like the blandishment of false philosophy, still offers glints of something darker beneath the surface. Soon, idealism will go astray, adolescence will be left to its own devices, children will be betrayed by insufficient parenting and the survivors will be made to pick through the rubble.

Ms. Bengson, a singer with enormous range both in pitch and timbre, is one of those survivors. Along with her husband, Shaun Bengson, she has written the music and lyrics for “The Lucky Ones,” and, with Sarah Gancher, its book. Their approach to the function of music in a musical is eclectic: It is sometimes simply presentational, as in a concert, sometimes narrative, sometimes (as with the use of hymns and folk songs) diegetic and sometimes a blend of all three.

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From left, Shaun Bengson on guitar, with Ms. Verson and Damon Daunno as a troubled couple, in “The Lucky Ones.”CreditSara Krulwich/The New York Times

This works quite well in the first part of the show, before the intermission, as I imagine it did in an earlier autobiographical Bengsons work, “Hundred Days,” about the first months of the couple’s marriage. “The Lucky Ones,” directed by Anne Kauffman, has a bigger cast and a hard-working ensemble (choreographed by Sonya Tayeh) to characterize the family and school community in small bites of song and recitative that get passed around like hors d’oeuvres. Myra Lucretia Taylor as Ms. Bengson’s mother, Ashley Pérez Flanagan as her sister Emily and Maryann Plunkett as her aunt do especially fine work making these archetypes specific.

But the story gradually focuses on Ms. Bengson’s cousin Kai (Damon Daunno) and Emma (Adina Verson), the new girl at school. (The names of almost all the characters, as well as some details of the plot and setting, have been altered.) Kai is the cool, questing stoner everyone crushes on; Emma is the wounded bird he finally falls for. Naturally, his family being so accepting and oblivious, they embrace the relationship even as it becomes clear that Kai is losing his grip.

Both Mr. Daunno and Ms. Verson are excellent, he pulsating with over-the-top teenage excitement, she shyly blinking in the glow of her good fortune. But as the first part of the show drags into the second, and nearly comes to a standstill in the third, the material falls out from under them.

The Bengsons’ songwriting, though feelingful, does not yet seem complex enough structurally to handle the size and depth of the action it must portray. The music, played by Abigail and Shaun — along with their band mates Dani Markham on drums and Pearl Rhein on keyboards, fiddle and accordion — has a pleasantly droning quality that forestalls harmonic development. The ruminative, repetitive lyrics similarly stunt the drama.

And then, too, the tale and its manner of telling take strange turns after the intermission, including a leap into the Bengsons’ own romance and a long section created from what we are told are verbatim transcripts of interviews with the family years after the events described. That these detours give the cast a chance to polish its naturalism does not make them useful in creating the feeling of a unified work. It’s a musical, after all.

Ms. Kauffman’s astute staging in the unusual Connelly space — it was once an orphans’ choir hall — does what it can to jury-rig a feeling of depth. She has an uncanny way of layering action, in this case not only within the proscenium but also in the former choir loft behind the audience. And Ms. Tayeh’s gestural dance language also supports the idea that something big and emotional is happening here.

But the storytelling is as yet too impulsive, and at times too self-indulgent, to be corralled in those ways. Perhaps with strong parenting “The Lucky Ones” will one day emerge more successfully, as “Hundred Days” did after a long development period. For now, like many an adolescent, it remains a gawky, powerful work in progress.